1. Field of the Invention
The present invention relates to an image display system comprising an information processing unit for processing image data and outputting an image signal, and an image display apparatus for receiving the image signal and displaying an image. More particularly, the present invention relates to an image display system in which an image display apparatus has coordinate input means for inputting position information on a display screen.
2. Description of the Related Art
Recently, there have been increased opportunities (e.g., in meetings, presentations and so on) for providing, to third parties, various types of data such as textual data, tables, and graphical data, which are prepared using application software for a personal computer. The various types of data can be provided (displayed) to the third parties using a large screen display (image display device), e.g., a front projector or a rear projector. In such a case, the display is connected to a video output terminal of the personal computer, and image data produced by the personal computer is displayed on a full-size screen of the display.
For the purpose of enhancing an appealing effect in meetings, presentations and so on, a part of an image displayed on a screen is often scaled up. This scaling-up is realized with a zoom function provided in the application software of the personal computer. Also, some displays have the zoom function in themselves. When utilizing the zoom function of the display itself, an image magnified at a certain scale-up rate about a screen position/screen coordinates, e.g., the screen center, as a base point is displayed by operating keys on the display or a remote control. Then, when an image position for scaling-up is to be shifted, a display area is shifted up, down, to the right or to the left by operating cursor keys on the display or the remote control.
A known system includes a digitizer (coordinate input device) capable of directly instructing coordinates on a display screen to display by an instruction means, such as a finger or a pen, and providing a pointing means with a similar function to that of a mouse of the personal computer.
There are various types of digitizers, including: a type having a pressure sensor within a display screen of the display which detects pressure caused upon contact of a pen, etc.; an electromagnetic induction type using a pen generating a magnetic field and detecting the magnetic field by a sensor disposed within a display screen; an ultrasonic surface elastic wave type having an ultrasonic transmitter and an ultrasonic sensor disposed in, e.g., a frame of a display screen, thereby detecting an object position on the display screen; and an infrared type using a pen emitting an infrared ray and receiving the emitted infrared ray by a sensor disposed within a display screen.
Any of the above-described types of digitizers can provide pointing information (position information) to the personal computer upon direct instruction on the display screen, and hence enables the personal computer to be operated in an intuitively matching way.
In cases such as described above, the digitizer and the personal computer are interconnected by an interface cable through which the pointing information is transmitted and received. Interface types include a serial interface used for connection of a mouse, a PS/2 interface, and a USB interface.
Driver software for reflecting the pointing information on the display screen, which is input through the interface cable, in movement of a cursor or the like is installed in the personal computer beforehand. As an alternative, such specific driver software is not needed if the pointing information from the digitizer is converted to standard mouse information.
An operating system (OS), e.g., Windows® 2000 made by Microsoft® runs in the personal computer. A plurality of windows for executing applications of a word processor and a spreadsheet, icons for starting up the applications, etc. are displayed on a display screen produced by the personal computer.
Further, a cursor image indicating a pointed position is produced on the display screen of the personal computer, and selection and movement of windows and icons are performed by instructing coordinates by the cursor.
When scaling up a part of the display image for the purpose of emphasis, however, resorting to the zoom function of applications installed in the personal computer, as described above, is disadvantageous because some of the applications do not have the zoom function.
When employing a display with the zoom function, a part of the display image can be scaled up without resorting to the applications installed in the personal computer, but it is hard to confirm the location of the current position of a scaled-up image. In addition, operations for displaying a scaled-up image and shifting a scale-up area after displaying the scaled-up image must be performed using the cursor keys on the display or the remote control. Thus, an intuitively matching operation cannot be performed.
On the other hand, a display provided with a digitizer is conceivable as one solution for providing the intuitively matching operation. However, coordinate pointing by such a digitizer provides only similar operations to those obtained by a mouse on the personal computer, and cannot perform the zoom function specific to the display and the operation for shifting a scale-up area after displaying a scaled-up image. Thus, convenience in use is not satisfactory.